Most rotary valves, such as butterfly valves, ball valves, and plug valves, require interconnecting elements between their automatic actuating devices having linear shaft movements and the rotating shafts of the valve itself.
Such interconnecting elements consist generally of a linkage having a primary opening which engages the valve shaft and a secondary opening, at some radial distance from the valve shaft center, to interconnect with a ball joint which in turn connects with a reciprocating spindle or actuator stem. The joint between this lever and the rotary valve shaft has to be strong to transmit substantial tortional forces during operation of the valve. In case of modulating control valves, there is an additional need to have this joint be free of any loose play or backlash. Any lost motion being highly detrimental to the positioning accuracy of the control system. Simple lever with a Woodruff key, engaging milled slots in either shaft and linkage, might be sufficient for transmission of torque for on/off valves. However, such method is highly unsatisfactory in case of modulating control valves.
Present state of the art devices utilize mechanisms to overcome these problems with precision milled and broached multi-splined shaft configurations. These levers, in addition, are split at least partially and clamped by means of suitable fasteners to prevent additional slippage. This method is reasonably satisfactory. However, it poses major disadvantages: First, the multi-spline machining operation is very complex and expensive due to the required tight tolerances and secondly, the disassembly of such a lever system after prolonged service in a corrosive atmosphere is very difficult. Thirdly, the angular alignment is very important and the availability of 30 or 40 spline positions tends to encourage wrongful angular alignment during assembly.
My invention overcomes all these disadvantages by providing a pair of identical linkages made from simple cast pieces without need of machining, which will slide loosely onto a square shaft configuration and which, by simply tilting towards each other, will tightly engage the shaft without backlash. The loosening of a simple fastener will restore the former loose engagement and will enable the levers to slide off the shaft even after prolonged corrosive service. Use of a square shaft configuration eliminates the possibility of angular error during assembly.
The object of this invention is to provide a very inexpensive simple, and reliable means of torque transmission for rotary control valves.
These and other advantages may be more readily understood when viewed in light of the following drawings: